Development criteria for ultraviolet disinfection of unfiltered drinking water

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Ultraviolet (UV) light has been shown to be effective against waterborne parasites such as Cryptosporidium and Giardia and is rapidly being adopted in water treatment for disinfection of filtered drinking water.   The use of UV for poor quality water sources, such as unfiltered surface water, has been limited because the effect of particles and other impurities in the water on the effectiveness of UV disinfection is poorly understood.   The broad objective of the proposed research is to improve the knowledge of how water quality variables such as microorganism concentration, particulate matter, and dissolved and colloidal organic matter, affect UV disinfection of microorganisms unfiltered natural water.  Aggregation and interaction of Cryptosporidium oocyst, Bacillus subtilis spores and other surrogate microorganisms with particles present in unfiltered natural water and synthetic water matrices will be investigated in laboratory experiments.  A method for conducting UV exposures with water samples containing low concentrations of seeded microorganisms will also be developed.   Because research with Cryptosporidium is very expensive and difficult, surrogate microorganisms will be used for UV inactivation studies.   Aggregation and particle-interaction of surrogate microorganisms in a variety of unfiltered natural water and synthetic water matrices will be measured and correlated with the level of inactivation measured in bench-top UV exposure experiments.  The anticipated end product of this research is a water quality index or a convenient standard test that could be used by water treatment engineers to predict the level of public health protection provided when UV is used to disinfect specific unfiltered water supplies.